Research activities in this laboratory are directed toward an understanding of the biology and evolution of extrachromosomal (plasmid) elements in Streptococcus ssp. Two major groups are currently being studied. S. faecalis which is a normal inhabitant of the large intestine and S. agalactiae which causes most neonatal sepsis and meningitis. We are carrying out genetic as well as molecular studies in order to characterize some of these elements. Three classes of plasmids have been described. First, large (50 x 10 to the 6th power d) self transmissible plasmids mediating bacteriocin production; these plasmids will transfer during matings in broth. Second, smaller (20 x 10 to the 6th power d) drug resistance factors that can transfer only when mated on solid support. Third, small (less than 6 x 10 to the 6th power d) resistance factors which can be mobilized by either class of sex factors. We are using combinations of in vivo and in vitro techniques to study both the nature of the cellular resistance. We are applying these same techniques. to the phenomenon of zonal lincomycin resistance which is plasmid mediated. By studying these two determinants in detail, we hope to obtain a better understanding of the evolution of drug resistance in gram-positive bacteria.